Materials
Dimethyl-1,2-benzenedicarboxylate, octane, n -propanol, andp -hydroxybenzaldehyde were provided from Aladdin, China. Ethyl acetate, ethanol, anhydrous sodium sulfate, copper sulfate, ferrous sulfate, zinc sulfate and magnesium sulfate were purchased from Tianjin Damao Chemical Reagent Factory, China. Sodium lignosulfonate and alkali lignin were supplied by Sigma-Aldrich, China. Organosolv lignin was obtained according to our previous study.26 Briefly, 10.0 g biomass feedstock (bagasse, poplar, bamboo or miscanthus powers), 1.2 g concentrated H2SO4 (Guangzhou Chemical Reagent Factory, China) and 150 mL 80% ethanol solution were placed into a 250 mL stainless autoclave and heated to 393 K at a stirring speed of 600 rpm. After 4 h, the autoclave was cooled rapidly under flowing water. Then, the reaction mixture was filtered, the filtrate was added into 500 mL deionized water for precipitating lignin. The solid (organosolv lignin) obtained by filtration was then dried under vacuum at 313 K for 12 h before use.